Three dimensional (3D) printing is a process of making three dimensional solid objects by ejecting ink toward a print surface. Typically an additive process is used wherein layers of the object being formed are successively printed and fused. The printing of 3D objects has the potential to significantly lower risks and costs of manufacturing. For example, using 3D printing, prototyping expenses can be significantly reduced and mass manufacturing of identical items is not necessary to recoup initial tooling startup investment. One interesting aspect of 3D printing is the formation of living tissue structures and organs using bio-inks.
Some 3D printed objects involve the printing of viscous inks. These viscous inks, which include bio-inks, require ejectors capable of efficiently printing viscous materials. In the case of bio-inks, the printing process needs to avoid shearing of cells and/or extracellular material.